In the past proposals have been made for parallel action toggle wrenches and one of these is shown in the 1967 patent to Burchett, but no provision is made therein for the varying of maximum pressure.
It is an object of this invention to provide not only for adjustment of the size of jaw opening at times when the handles are drawn together and the toggle fully pressured, but also for the adjustment of the amount of maximum pressure to be applied on an object.
At the present time toggle pliers are popular on the market, but not toggle wrenches. A toggle pliers has jaws, the compression surfaces of which are almost always disposed at an angle to each other, and not in parallelism. Bolt heads and nuts all have flat surfaces, between which there are corners which can become chewed off when toggle pliers are used, until they are unfit to be worked with by means of a wrench.
A wrench without a means for applying pressure between its jaws likewise tends to round the corners of another bolt because of the lack of tight fit of the wrench against another bolt.
It is very important that there be made available a concept of a wrench, the compression surfaces of the jaws of which are parallel at all times, but that also has means for applying substantial pressure on a nut or bolt to prevent the jaws from slipping around the corners of a nut or bolt.